This application relates to a method for soil remediation, and in particular to the concurrent removal of hydrocarbon contaminants and heavy metal fixation.
Contamination of soil by hazardous organic pollutants and/or heavy metals is a serious environmental problem facing the global community. Over time, these pollutants, trapped in the soil matrix, leach through inadequate holding facilities and migrate deep into the earth, finally making their way to groundwater aquifers. Once contaminated, these aquifers carry the toxins through the ecological system, bringing them into the food chain.
Typically, both heavy metals and hydrocarbon contaminants are associated with the finer particle fractions of soils and sediments. Most techniques for the removal of metals involve contacting the soil with an aqueous solution. Similarly, some processes remove hydrocarbon contaminants by aqueous washing methods. For fine textured, high clay soils these techniques tend to produce intractable sludges having poor solid-liquid separation characteristics. Other soil cleaning technologies, such as thermal desorption, are also poorly suited for treating fine textured top soils because of adverse effects on the associated humic matter or soil mineralogy. In such cases the treated soil may have to be landfilled or used as subsoil because of impaired soil fertility.